substracting multiple self-intersecting helix 2

[kukelyk]

Hi.
I have to model a pulley with variable pitch.
I have the shaft, and the helix body, with the variable pitch.
The first 4 turns of the helix the pitch smaller than the diameter of the 'spring', what causes multiple self-intersecting body.
I need to substract the helix from the shaft, but after the substraction, the model falls apart.
I tried to split the helix and substract its pieces, but then the same thing happens.
Is there a way to simplify the helix body?
Any help would be appreciated


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kukelyk

 

[kukelyk]

(i am on NX4.04)

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kukelyk

 

[hudson888]

Just post a model or maybe a picture of what you want.

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum

 

[kukelyk]

Here is a picture, it is a section of the 2 bodies.
My job is the green shaft.

http://files.engineering.com/getfile.aspx?folder=7ac99ee0-ba6d-4cab-88e5-3455049ccf24&file=csiga.JPG

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kukelyk

 

[kukelyk]

When i try to split the helix, and substract them from the shaft, i get the next error message:
"Thru face does not intersect path of the tool"
i see the interference between them, so i got confused..

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kukelyk

 

[mmauldin]

I tried to create a similar file and found that if subtracting the helix breaks the cylindrical face of the cylinder the model fails.

Attached is a zip with jpegs of the model with the cylinder wall intact and without, plus the model file I used to get the result.

I don't how this helps (maybe it doesn't), but is this the failure you are seeing?

 

[kukelyk]

yes. this is the problem.
thanks for your pains
do you have any suggestion?

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kukelyk

 

[hudson888]

I have managed to get a result for you. It is somewhat unsatisfying but nevertheless it is a viable solution. I noted that the tube where it self intersects does not internally unite with itself. So by splitting up the helix into several segments in this case you're able to avoid the coils from individually overlapping by ensuring in the first two that they never complete a full revolution.

I tried the same thing all the way through with a law controlled sweep of a circular section finding the same problem as the helix, so I'll save you the bother on that account.

I hope you are in some small part better off for this solution.

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum

 

[kukelyk]

many thanks. i try to go on

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kukelyk